Murphy's laws of cryptography

• Cryptography turns a security problem into a key management problem.
• New cryptography generates new attacks.
• If it's provably secure, it's probably not.
• Any large enough system will include broken cryptography.
• Any attempt to standardize will instead lead to massive fragmentation.
• Any new standard is obsolete.
• Broken in theory does not imply broken in practice, and vice-versa.
• There's always a trusted third-party.
• What sounds like a solution now will create more problems later:
  • "Just use an HSM."
  • "Assume a PKI is available."
  • "Assume a broadcast channel."
  • "Assume little-endianness."
• Come for the cryptography, stay for the DER and PEM encodings.
• Any new cryptography API will use different conventions than all existing cryptography APIs.

As crowdsourced on Twitter. See other Murphy's laws.